The following disclosure relates to image producing machines, and more particularly to solid ink machines that use a phase change ink melting and control apparatus.
In general, phase change ink image producing machines, such as printers, employ phase change inks that are in the solid phase at ambient temperature, but exist in the molten or melted liquid phase (and can be ejected as drops or jets) at the elevated operating temperature of the machine or printer. At such an elevated operating temperature, droplets or jets of the molten or liquid phase change ink are ejected from a printhead device of the printer onto a printing media. Such ejection can be directly onto a final image receiving substrate, or indirectly onto an imaging member before transfer from it to the final image receiving media. In any case, when the ink droplets contact the surface of the printing media, they quickly solidify to create an image in the form of a predetermined pattern of solidified ink drops.
An example of such a phase change ink image producing machine or printer, and the process for producing images therewith onto image receiving sheets is disclosed in U.S. Pat. No. 6,905,201, issued on Jun. 14, 2005, to Leighton et al., the disclosure of which is incorporated herein by reference. As disclosed therein, a high-speed phase change ink image producing machine, such as printer 10 shown in FIG. 1, includes a frame 11 to which are mounted directly or indirectly all its operating subsystems and components. One of the components is an imaging member 12 that is shown in the form of a drum, but can equally be in the form of a supported endless belt. The imaging member 12 has an imaging surface 14 that is movable in the direction 16, and on which phase change ink images are formed.
The high-speed solid ink printer 10 also includes a phase change ink system 20 that has at least one source 22 of a single color phase change ink in solid form. When the printer 10 is a multicolor image producing machine, the ink system 20 includes four sources 22, 24, 26, 28, representing four different colors CYMK (cyan, yellow, magenta, black) of phase change ink solid pieces, as shown in FIG. 1. The phase change ink system 20 also includes a solid phase change ink melting and control assembly or apparatus 100 (FIG. 2A) for melting or phase changing the solid form of the phase change ink into a liquid form, and for then supplying the liquid form to the printhead system 30. The printhead system 30 includes at least one printhead assembly 32, or in the case of a high-speed, or high throughput, multicolor image producing machine, four separate printhead assemblies 32, 32, 36 and 38, as shown in FIG. 1.
The solid ink image producing printer 10 further includes a substrate supply and handling system, which may, for example, include multiple substrate supply sources 42, 44, 46, 48. The substrate supply and handling system further includes a substrate treatment system 50 that has a substrate pre-heater 52, substrate and image heater 52, and a fusing device 60. The phase change ink image producing printer 10 as shown may also include an original document feeder 70 that has a document holding tray 72, document sheet feeding and retrieval devices 72, and a document exposure and scanning system 76.
Operation and control of the various subsystems, components and functions of the machine or printer 10 are performed with the aid of a controller or electronic subsystem (ESS) 80. The ESS or controller 80 for example is a self-contained, dedicated mini-computer having a central processor unit (CPU) 82, electronic storage 82, and a display or user interface (UI) 86. The ESS or controller 80 for example includes sensor input and control means 88 as well as a pixel placement and control means 89. In addition the CPU 82 reads, captures, prepares and manages the image data flow between image input sources such as the scanning system 76, or an online or a work station connection 90, and the printhead assemblies 32, 32, 36, 38. As such, the ESS or controller 80 is the main multi-tasking processor for operating and controlling all of the other machine subsystems and functions, including the machine's printing operations.
In operation, image data for an image to be produced is sent to the controller 80 from either the scanning system 76 or via the online or work station connection 90 for processing and output to the printhead assemblies 32, 32, 36, 38. The controller determines and/or accepts related subsystem and component controls, for example from operator inputs via the user interface 86, and accordingly executes such controls. As a result, appropriate color solid forms of phase change ink are melted and delivered to the printhead assemblies. Additionally, pixel placement control is exercised relative to the imaging surface 12 thus forming desired images per such image data, and receiving substrates are supplied by anyone of the sources 22, 22, 26, 28 and handled by means 50 in timed registration with image formation on the surface 12. Finally, the image is transferred within the transfer nip 92, from the surface 12 onto the receiving substrate for subsequent fusing at fusing device 60.
In certain machines, the phase change ink system 20 includes a solid phase change ink melting and control apparatus 100 (FIG. 2A), including a pre-melter assembly 200 and a melter assembly 300. The pre-melter assembly 200 is suitable for controllably supplying solid pieces of phase change ink from the sources 22, 22, 26, 28 (FIG. 1) to the melter assembly 300 located below the pre-melter assembly 200, and more particularly to the separate melters 300A-D. A melted molten liquid ink storage and control assembly 400 is located below the melter assembly 300.
In high throughput solid ink systems, the storage and control assembly 400 may incorporate a dual reservoir system corresponding to each of the individual melters 300A-D for the various colors implemented in the solid in system. In this system, molten liquid ink is fed from a corresponding melter 300A-D into an associated primary reservoir 404A-D, which stores a first volume of melted ink for subsequent use. This reservoir is connected through a check valve or backflow prevention valve assembly 408 to a corresponding secondary reservoir 406 which stores a second volume of melted liquid ink. The liquid ink is ejected from the storage and control assembly 400 at an outlet array 410 and typically fed through a heated routing system to reach a respective printhead or printheads of the printhead assembly 30. In systems of this type, pressure is applied at particular ones of the secondary reservoirs 406 to discharge ink through a corresponding outlet 410, such as through a piston or pressurized air arrangement. The check valve assembly 408 prevents backflow of liquid ink from the now pressurized secondary reservoir back into the primary reservoir 404.
In a typical prior art system, the check valve assembly 408 includes an individual check valve for each primary reservoir 404A-D. Although each check valve is integrated into a common housing, the check valve itself is usually an off-the-shelf single valve that is supported within the housing. The check valves of the prior art are often ball valves, although needle and flapper or disc valves have also been used. The nature of the check valves used in prior art systems places significant limitations on the size of the valve assembly 408. In other words, the nature of these prior check valve configurations requires a certain amount of space or a particularly large envelope so that a reduction in space requirements are not a viable option. Limitations on the “smallness” of the space requirements for the check valve assembly 408 cascades into limitations on the size and positioning of the first and second reservoirs 404, 406 served by the valve assembly.
Another difficulty with the check valve assemblies used in prior art machines is that they are typically formed of stainless steel. These stainless steel components require a warm-up time that is not conducive to a high speed, quick reacting printing machine. Since the printing machine utilizes molten ink, all of the components must be “at temperature” when the machine is operated to maintain ink in its molten state. Bringing the check valve assembly to temperature is particularly important since any partially solidified ink within the valve assembly can hold the check valve in an open or closed position, thereby destroying the functionality of the particular check valve.
There is a need for a check valve assembly that is readily scalable depending upon the nature of the printing machine. Such a check valve assembly should also be easy and inexpensive to manufacture, without sacrificing, and preferably improving, flow of molten ink through the valve.